1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, more particularly to an electrophotographic photosensitive member which comprises a photosensitive layer containing an azo pigment of a specified chemical structure.
The present invention also relates to an electrophotographic apparatus and a facsimile machine employing the photosensitive member
2. Related Background Art
Electrophotographic photosensitive members composed of an organic photoconductive substance include photoconductive polymers typified by poly-N-vinylcarbazole, low-molecular organic photoconductive substances like 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, and combinations of such an organic photoconductive substance with a dye or a pigment.
Electrophotographic photosensitive members employing an organic photoconductive substance have advantages that the photoconductive members are producible by a coating method with high productivity at a relatively low cost, and that the electrophotographic characteristics thereof is arbitrarily controlled by selecting the dye or the pigment to be used. Therefore, the electrophotographic photosensitive members have comprehensively been investigated. Recently, function-separation type photosensitive members have been developed which have a lamination structure comprising a charge-generating layer containing an organic photoconductive dye, a pigment, or the like and a charge-transporting layer containing aforementioned photoconductive polymer or a low-molecular organic electroconductive substance. The development of the function-separation type ones has improved remarkably the sensitivity and the durability of conventional organic electrophotographic photosensitive members.
Among organic photoconductive substances, many azo pigments have superior photoconductivity generally. Moreover, various properties of the azo pigments can readily be obtained by selecting the combination of the azo component and the coupler component. Accordingly, many azo pigments have been reported as charge-generating substances, for example, in Japanese Patent Application Laid-Open Nos. 57-116345 and 58-95742, and so forth.
Recently, to meet the demand for higher picture quality and higher durability, electrophotographic photosensitive members are being investigated for better characteristics thereof.